Understanding Antibody Testing for COVID-19

Abstract

The orthopedic community has seen the COVID-19 pandemic decimate elective surgical volumes in most geographies. Patients and essential workers, such as health care providers, remain rightfully concerned about how to appropriately begin to return to work and community activity in a safe and responsible manner. Many believe that testing for the presence of antibodies on a widespread scale could help drive evidence-based decision-making, both on an individual and societal scale. Much information, and an equal amount of misinformation, has been produced on antibody testing. Education about the role and science of such testing is critically important for programs to be effectively understood and managed.

Keywords: COVID; COVID-19; PCR; antibodies; antibody; coronavirus; screening; testing.

Fig. 1

The typical lateral flow immunoassay cassette with a control band “C” and two antibody indicators. The “M” band indicates the presence of IgM and “G” band indicates IgG is detected. For a test to be considered valid, the control band must be present. Therefore, the test cassette on the left would be considered a negative test result (control band and no antibody bands), whereas the cassette on the right would be an invalid result (lack of control band, despite both antibody bands being present).

Fig. 2

Lateral flow immunoassay cassette with positive IgG. In both of the cassettes, the IgG band is detectable and the control band is present. This indicates a valid test confirming the presence of IgG to the target antigen. Color intensity should not be interpreted quantitatively and both images are considered a positive result.

Fig. 3

Lateral flow immunoassay cassette with positive IgM. In both of the cassettes, the IgM band is detectable and the control band is present. This indicates a valid test confirming the presence of IgM to the target antigen. Color intensity should not be interpreted quantitatively and both images are considered a positive result.

Fig. 4

Lateral flow immunoassay cassette with both IgM and IgG positive. This cassette shows a case where both IgM and IgG bands are present, in addition to the control band. This is a valid test that has detected the presence of two different antigens, one with affinity to IgM and a second with affinity to IgG antibodies.